but guys, its just dark brown! The nice purpley bits at the ends are the remnents of my old colour. I have always thought lighter hair looks betteron me!
Maybe it does look better, who knows. But when you consider your hair, you have to consider how it'll look in relation to the rest of you, including what you wear. At the moment, darker hair looks great with the clothes you wear, which are mostly dark with some light contrasting colours. If you decide again to be bright red on top, then you'd have to switch to lighter clothes with few dark colours. Basically, what you're wearing in that last picture, but with the red and black inverted. Otherwise, your head could be distracting, which isn't always a good thing. You have a nice skin tone, which is complimented by your dark hair. I'm not sure bright red is a colour that would work as well with your skin.
You shouldn't consider any of this too much (at all), it's just my personal taste. I like peoples appearances to have a sort of uniformity instead of just colour splashed all over the place. I find the most attractive girls are the ones who dress and style themselves to compliment their best features, and one of yours is your face. The dark hair creates a nice 'frame' for that which I'm not sure beacon red would accomplish so well.